As the power and speed of computers has grown, so has the ability to provide computer-generated artificial and virtual environments. Such virtual environments have proven popular for training systems, such as for driver training, pilot training and even training in performing delicate medical and surgical procedures. These systems typically involve combining prerecorded or computer generated visual information with a real world environment to provide the perception of a desired environment. For example, a driver's training simulator may include a physical representation of the driver's seat of an automobile with a video or computer generated image of a road and traffic projected on what would be the windshield of the simulator car of a student driver. The image is made to be reactive to the actions of the driver, by changing speeds and perspectives in response to acceleration, braking and steering by the driver. Similarly, sophisticated flight simulators include a physical cockpit and projected flight environments that present real world situations to the pilot via a display.
In some cases, a virtual reality is projected in front of the eyes of a user via a virtual reality helmet, goggles, or other input device, so that the only image seen by the user is the virtual image. In other instances, mirrors and partially reflective materials are used so that a user can view both the real world environment and the virtual environment at the same time.
A disadvantage of prior art virtual reality and simulation systems is difficulty in combining real world and virtual world images in a realistic and unrestricted manner. In some prior art cases, certain views and angles are not available to a user because they require prior calculation of image perspective and cannot be processed in real time. In other instances, the ability to interact with the virtual world with physical objects is limited or unavailable.